Plan, adapt and learn from quality inspections

A lack of adaptation of inspection processes in production often leads to excessive quality costs. On the one hand, inspection processes for non-critical characteristics, which are already secured by stable and capable manufacturing processes, cause unnecessarily high inspection costs. On the other hand, defective products in the field or in production indicate ineffective or missing inspection processes and result in increased defect costs. The mentioned potentials for reducing quality costs remain unused in many companies. There are many sources of information that provide information about missing, ineffective or superfluous quality inspections. These sources include, for example, information from complaints processes, internal defect correction, or inspection data evaluation. These sources must be identified, their information processed, and transferred in a structured manner to inspection planning in order to enable the continuous and systematic adjustment of quality inspections during the manufacturing phase of a product.

Test planning knowledge often remains unused

In addition to the often inadequate adaptation of inspection processes according to the quality situation in production and in the field, the systematic use of empirical knowledge represents a major challenge for corporate inspection planning. Despite the increased use of CAQ systems and preventive quality methods, such as the concept of special characteristics in product development or failure mode and effects analysis (FMEA) in quality planning, test planning is a knowledge-intensive corporate process whose success is based to a large extent on the functioning use and transfer of empirical knowledge. If quality tests are adapted in the manufacturing phase of a product on the basis of individual events (e.g. safety-critical faults in the field), this adaptation knowledge is seldom used for the test planning of similar products or subsequent product generations. There is often a lack of suitable structures and procedures to transfer the empirical knowledge from the manufacturing phase to the test planning accompanying the development. This leads to repeated planning errors, which in turn result in unnecessarily high quality costs. Consequently, the targeted transfer of methods and tools of knowledge management is required in order to make empirical knowledge available in test planning and to use it for subsequent planning activities.

Holistic test planning

In order to meet the above-mentioned challenges, the practice-oriented research project "P² - Use of reactive process data for holistic inspection planning " was carried out at the Machine Tool Laboratory WZL of RWTH Aachen University. The aim of the project was the provision and use of data of reactive processes (e.g. test data evaluation, defect elimination processes, complaint processes) in test planning in order to be able to carry out a continuous and comprehensive adaptation of quality tests in the manufacturing phase. In order to establish a learning test planning, it was necessary to make the knowledge resulting from the adaptation available for the test planning of subsequent product and process development projects.

Within the scope of the research project, a process concept for holistic test planning was developed and elaborated, which is shown in the figure. This comprises the four process areas "test planning during development", "test planning during production", "networking of test planning processes" and "improvement management".

Test planning during development

The development-accompanying test planning comprises the classical test planning, which is initially carried out in the course of the product and process development. The task steps and methods are already described comprehensively in the quality management literature. In addition to the existing procedure of test planning, a comprehensive process and data catalog with test planning-relevant input data from different phases of product development was developed within the framework of the project, which simplifies the procurement and provision of information for test planning.

Production-accompanying test planning

When the product enters the manufacturing phase, there are various reasons for adapting quality tests. This is the task of test planning during production. For this purpose, a reference process for the adaptation of existing test processes was developed based on existing process concepts of change management. This enables companies to initiate the change of inspection processes on the basis of various change triggers, to plan and evaluate potential change options, and to plan and evaluate the change of inspection processes on the basis of various change triggers.

The potential for reducing quality costs often remains unused.

The concept of holistic test planning extends the scope of test planning to the product manufacturing phase. In this way, the concept of holistic test planning extends the scope of test planning to the product manufacturing phase. The object of inspection planning is thus no longer merely the planning of inspections as part of the product development process, but also the adaptation of quality inspections when changes are required in production.

Networking of the test planning processes

When quality tests are adapted in the manufacturing phase, knowledge relevant to test planning is generated, which can be used for similar products or future development projects. It is therefore necessary to link the processes of test planning in the manufacturing phase and the product development process in such a way that the generated knowledge can be stored, distributed and used. For this purpose, a framework was derived based on knowledge management procedures and models, which provides targeted recommendations for the generation, storage, distribution and application of empirical knowledge in test planning.

Improvement management

To support the company-specific introduction of the reference processes, the holistic test planning was supplemented by the area of improvement management. By applying the PDCA cycle (Plan, Do, Check, Act), weaknesses in the implementation or operation of the inspection planning processes can be identified and remedied, leading to continuous optimization of the inspection planning processes in development and manufacturing.

Optimized quality inspection

By monitoring and analyzing reactive process data in the manufacturing phase of a product, companies can estimate the benefits and effort required to adapt quality inspections and implement them using a suitable methodology. In addition to the systematic adjustment of quality inspections in the manufacturing

Avoid repetition errors.

The project investigated the extent to which methods and tools of knowledge management can be transferred to test planning in order to make the knowledge gained from the adaptation of quality tests available to those involved in test planning in product and process development. Through a continuous knowledge transfer and anchoring of this knowledge in test planning, repetitive errors in the planning and design of quality tests can be avoided and thus unnecessary adjustments of test processes in the manufacturing phase can be saved.

Acknowledgements

The procedure was developed within the framework of the research project "P² - Utilization of reactive process data for holistic inspection planning (17 584 N)", which was funded by the AiF Arbeitsgemeinschaft industrieller Forschungsvereinigungen "Otto von Guericke" e.V. (German Federation of Industrial Research Associations). The project was supervised by the Research Association for Quality (FQS) of the German Society for Quality (DGQ). (DGQ). The voice of practice was represented in the project by a project-accompanying committee, to which various companies belonged. The members included DORMA Deutschland GmbH, Franz Kessler GmbH, Heim&Haus Produktionsgesellschaft mbH, Ph-MECHANIK GmbH & Co. KG and Rhein-Getriebe GmbH (names in alphabetical order). The authors would like to thank all participants for the very good and successful cooperation.